lex.c.blt: update

	* lex.c.blt: follows r52429, not removing casts to int.
	* defs/keywords (alias, undef): symbol literals are allowed.

	* parse.y (parse_percent): should parse symbol literals for alias
	  and undef.  [ruby-dev:47681] [Bug #8851]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@54642 b2dd03c8-39d4-4d8f-98ff-823fe69b080e